Electrostatic actuation is the most prevalent means of driving micro electro-mechanical systems (MEMS) devices. State-of-the-art MEMS devices utilizing electrostatic actuation include: inertial sensors such as Analog Devices ADXL™ [1]; pressure sensors; RF switches and filters; MEMS displays such as TI-DLP™ [2], Silicon Light Machines' Grating Light Valve™ (GLV™) [3], optical cross-connect, e.g., Lucent LambdaRouter™ [4] and more.
The emerging technology of scanning micro-mirrors enables the processing of relatively compact and low cost digital and analog light. Among such applications are the Texas Instruments DLP™ used for modern, state of the art displays and the Lucent double-gimbaled WaveStar™ micro-mirror used in optical communication state-of-the-art all-optics routers. Other applications include barcode scanners, scanning confocal microscope, scanning for direct display on retina and more. A gimbal is a device that permits a body to incline freely around a predetermined axis, or suspends it so that it will remain level when its support is tipped.
In many MEMS applications multi-axis drive and control of deformable elements is required. Double-gimbaled micro-mirrors have been developed in order to achieve scanning in two dimensions. In state of the art double-gimbaled micro-mirror technology, the actuation of the two degrees of rotation is coupled due to electrostatic coupling effects. For example, the Lucent LambdaRouter™ uses a double-gimbaled micro-mirror to route optical information from a source fiber into a 2D array of target fibers. The electrostatic coupling between the two axes of rotation causes distortion of the picture that requires special linearization algorithms to reconstruct the correct rectangular domain. Moreover, the calibration has to be carried out for each individual device to account for its specific electromechanical properties. This in turn, increases the cost associated with these devices.
The principle of setting an element on a multi-gimbaled frame is well known, e.g., for use in traditional rotation gyroscopes. However, the use of electrostatic actuation to drive the gimbaled devices, results in a nonlinear coupling between the axes. As a result, the scan range becomes distorted [5]. Many control techniques have been proposed to deal with this nonlinear coupling effect. However, all such prior art has further complicated the calibration and operation of the device.
Therefore, there is a need in the art to provide a simpler device and method that avoids nonlinear coupling between the axes, when using electrostatic actuation to drive dual axes devices.